Vehicles including belt alternator starters are known in the art. They are distinguished by the following features:
a) rigid pulleys including torsional vibration dampers (TVD)
b) pulley decouplers (PYD) including a torsional vibration damper
c) magnetic friction clutches for auxiliary units
Only alternative c) allows the operating point of a crankshaft separation to be determined. For reasons of installation space, however, no combination with a pulley decoupler is possible. By means of a friction clutch, the combustion engine is started out of a stationary air-conditioning in a more immediate way as what is referred to as an impulse start.
A disadvantage of the known solutions is that no stationary or stop air conditioning is possible because the belt drive cannot be mechanically decoupled from the crankshaft. The interior temperature rises during start/stop operations and there is a CO2 disadvantage in the case of an early restart of the combustion engine. If magnetic clutches are used, no combination with a PYD is possible.
In vehicles including a belt alternator starter (BAS) and an accessory power take-off that can be decoupled, the belt drive may be operated electrically by an electrical motor (e-motor) when the engine is at a standstill for instance to implement air-conditioning when the engine is switched off or at a standstill. This operating point occurs, for instance, in stop phases at traffic lights or in sailing or coasting mode. A quick re-start of the combustion engine out of this operating condition is imperative.
Friction clutches (for instance magnetic clutches) generally meet this requirement because the rotary speed differences that occur are compensated for by slip, allowing the combustion engine to be started immediately (impulse start). However, these clutches are impossible to be combined with pulley decouplers (PYD) for installation space reasons.
The published German Patent Application DE 10 2011 081 121 A1 discloses a pulley assembly with a system of ramps for decoupling a pulley from a drive shaft when the drive shaft is at a standstill and a means of traction interacting with the pulley is driven counter to the driving direction, in particular with the aid of an electric machine, for instance a starter alternator. The published German Patent Application DE 10 2012 208 318 A1 discloses a belt drive with a crankshaft pulley and a starter alternator. The disclosed solution provides stationary air-conditioning by a reverse rotation of the starter alternator. When the crankshaft is at a standstill or is rotating slowly, for instance in stationary air-conditioning and starting operations, a centrifugal-force clutch is open and does not transmit torque.